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Electrochemical characterization of hydroxylated xanthones by cyclic voltammetry

Santos, Clementina M.M.; Garcia, Beatriz; Silva, Artur; Cavaleiro, José; Fernandes, Eduarda
Fonte: Instituto Politécnico de Bragança Publicador: Instituto Politécnico de Bragança
Tipo: Conferência ou Objeto de Conferência
Português
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Xanthones constitute a class of oxygenated heterocyclic compounds commonly identified in some higher plant families, fungi and lichens [1]. Their large variety of biological and pharmacological activities encouraged the scientific community for the search and isolation of natural derivatives for therapeutic applications [2]. Consequently, extensive studies have been devoted to the development of synthetic routes for the preparation of these naturally-occurring compounds or other synthetic bioactive derivatives [3,4]. For the present study, xanthones XH1-9 were obtained by synthesis and the diversity of substitution pattern includes the presence of phenolic and catecholic moieties. These structural features are important requisites for the scavenging activity against reactive oxygen and nitrogen species already demonstrated by these molecules [5]. During the last decades, electrochemical studies have been widely used for the evaluation of structure-antioxidant activity relationship of several phenolic compounds [6,7]. Thus, the electrochemical profile of xanthones XH1-9 can provide useful information about their electrochemical reactions, which may be used to predict or explain their biological properties. In this communication we will report the electrochemical characterization by cyclic voltammetry of various hydroxylated xanthones...

Xantonas oxigenadas bioativas: cristalização, estrutura e suas interações intra e intermoleculares; Bioactive oxygenated xanthones: crystallization, structure and their intra- and intermolecular interactions

Corrêa, Rodrigo de Souza
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 29/07/2009 Português
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As xantonas compreendem uma importante classe de heterocíclicos moleculares que possuem um esqueleto dibenzo-gama-pironas, podendo estes serem obtidos tanto por meios sintéticos quanto naturais. Estes constituintes têm sido freqüentemente isolados de plantas medicinais brasileiras e vêm recebendo atenção devido a seus aspectos fitoquímicos e suas propriedades biológicas. No entanto, poucos estudos são dedicados à abordagem estrutural mais aprofundada desses compostos no estado sólido, principalmente com relação a estudos cristalográficos. Uma justificativa para a escassez de trabalhos dessa natureza pode estar relacionada com a dificuldade de obtenção de cristais de qualidade. Com isso, a primeira etapa deste trabalho dedicou-se à obtenção de monocristais dos derivados xantônicos e, posteriormente, realizaram-se as medidas de difração de raios X por monocristal. Após a coleta de dados de difração de raios X, as estruturas cristalinas foram resolvidas e refinadas. Neste trabalho estudaram-se doze estruturas cristalinas de derivados xantônicos oxigenados, sendo que, uma das xantonas tetra-oxigenadas apresentou dois polimorfos. Portanto, onze constituintes quimicamente diferentes estão envolvidos (I-XI). Ressalta-se que das doze estruturas determinadas por difração de raios X apenas uma...

Estrogenic and chemopreventive activities of xanthones and flavones of Syngonanthus (Eriocaulaceae)

De Oliveira, Ana Paula Siqueira; De Sousa, Juliana Ferreira; Da Silva, Marcelo Aparecido; Hilário, Felipe; Resende, Flávia Aparecida; De Camargo, Mariana Santoro; Vilegas, Wagner; Santos, Lourdes Campaner Dos; Varanda, Eliana Aparecida
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 1053-1063
Português
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The possible benefits of some bioactive flavones and xanthones present in plants of the genus Syngonanthus prompted us to screen them for estrogenic activity. However, scientific research has shown that such substances may have undesirable properties, such as mutagenicity, carcinogenicity and toxicity, which restrict their use as therapeutic agents. Hence, the aim of this study was to assess the estrogenicity and mutagenic and antimutagenic properties. We used recombinant yeast assay (RYA), with the strain BY4741 of Saccharomyces cerevisiae, and Ames test, with strains TA100, TA98, TA97a and TA102 of Salmonella typhimirium, to evaluate estrogenicity, mutagenicity and antimutagenicity of methanolic extracts of Syngonanthus dealbatus (S.d.), Syngonanthus macrolepsis (S.m.), Syngonanthus nitens (S.n.) and Syngonanthus suberosus (S.s.), and of 9 compounds isolated from them (1 = luteolin, 2 = mix of A-1,3,6-trihydroxy-2-methoxyxanthone and B-1,3,6-trihydroxy-2,5- dimethoxyxanthone, 3 = 1,5,7-trihydroxy-3,6-dimethoxyxanthone, 4 = 1,3,6,8-tetrahydroxy-2,5-dimethoxyxanthone, 5 = 1,3,6,8-tetrahydroxy-5- methoxyxanthone, 6 = 7-methoxyluteolin-8-C-β-glucopyranoside, 7 = 7-methoxyluteolin-6-C-β-glucopyranoside, 8 = 7,3′-dimethoxyluteolin- 6-C-β-glucopyranoside and 9 = 6-hydroxyluteolin). The results indicated the estrogenic potential of the S. nitens methanol extract and four of its isolated xanthones...

Xanthone biosynthesis in Hypericum perforatum cells provides antioxidant and antimicrobial protection upon biotic stress

Franklin, Gregory; Conceição, Luís F. R.; Kombrink, E.; Dias, Alberto Carlos Pires
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2009 Português
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Xanthone production in Hypericum perforatum (HP) suspension cultures in response to elicitation by Agrobacterium tumefaciens co-cultivation has been studied. RNA blot analyses of HP cells co-cultivated with A. tumefaciens have shown a rapid up-regulation of genes encoding important enzymes of the general phenylpropanoid pathway (PAL, phenylalanine ammonia lyase and 4CL, 4-coumarate:CoA ligase) and xanthone biosynthesis (BPS, benzophenone synthase). Analyses of HPLC chromatograms of methanolic extracts of control and elicited cells (HP cells that were co-cultivated for 24 h with A. tumefaciens) have revealed a 12-fold increase in total xanthone concentration and also the emergence of many xanthones after elicitation. Methanolic extract of elicited cells exhibited significantly higher antioxidant and antimicrobial competence than the equivalent extract of control HP cells indicating that these properties have been significantly increased in HP cells after elicitation. Four major de novo synthesized xanthones have been identified as 1,3,6,7-tetrahydroxy-8-prenyl xanthone, 1,3,6,7-tetrahydroxy-2-prenyl xanthone, 1,3,7-trihydroxy-6-methoxy-8-prenyl xanthone and paxanthone. Antioxidant and antimicrobial characterization of these de novo xanthones have revealed that xanthones play dual function in plant cells during biotic stress: (1) as antioxidants to protect the cells from oxidative damage and (2) as phytoalexins to impair the pathogen growth.; Fundação para a Ciência e a Tecnologia (FCT) - POCTI/AGR/40283/2001...

Novel methods to extract flavanones and xanthones from the root bark of Maclura pomifera

Teixeira, Dora; Costa, Cristina
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Português
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A comparison between the extraction yields of xanthones and flavanones from the root bark of the Maclura pomifera by solid-liquid extraction (SLE), matrix solid phase dispersion (MSPD), and an alternative method using sea sand as a sample disruptor, is presented here. Two extraction solvents were used for all extraction techniques, dichloromethane and methanol:water, (9:1, v/v). The extraction procedures were reproducible as the R.S.D. values were less than 5% for almost all compounds. A recovery above 80% was obtained for macluraxanthone using the sea sand extraction procedure. Statistical treatment, ANOVA-single factor, was used to evaluate the different extraction procedures, and homogenization of plant material with sand followed by elution with dichloromethane provided the most efficient and rapid extraction method.

New syntheses of potential biologically active xanthones and benzoxanthones

Rocha, Djenisa H. A.; Leal, Stephanie B.; Seca, Ana M. L.; Pinto, Diana C. G. A.; Silva, Artur M. S.
Fonte: SPQ Publicador: SPQ
Tipo: Conferência ou Objeto de Conferência
Publicado em /09/2013 Português
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10º Encontro Nacional de Química Orgânica e 1º Simpósio Luso-Brasileiro de Química Orgânica, Lisboa, 4-6 Setembro de 2013.; The synthesis of xanthones, adequately functionalized for a specific application, is a challenging task. In this presentation, will be disclosed our recent studies with this unique family of compounds, namely the one-pot photoinduced electrocyclisation of (E)-3-styrylflavones 1 and in situ oxidation of cycloadducts to give 5-phenyl-7H-benzo[c]xanthen-7-one derivatives 2,3a and aromatization studies of (E)-3-aryl-4-benzylidene-8-hydroxy-3,4-dihydro-1H-xanthene-1,9(2H)-diones 33b into 4-benzyl-1,8-dihydroxy-3-phenyl-9H-xanthen-9-one derivatives 4.

Antibacterial xanthones from Kielmeyera variabilis mart. (Clusiaceae)

Pinheiro,Lucimar; Nakamura,Celso Vataru; Dias Filho,Benedito Prado; Ferreira,Antonio Gilberto; Young,Maria Claudia Marx; Cortez,Aparicio Garcia
Fonte: Instituto Oswaldo Cruz, Ministério da Saúde Publicador: Instituto Oswaldo Cruz, Ministério da Saúde
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2003 Português
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The bioassay-guided fractionation of stems from Kielmeyera variabilis, traditionally used in Brazilian folk medicine, yielded assiguxanthone-B (1), kielcorin (4), 2,5-dihydroxybenzoic acid (3), and a mixture of xanthones containing assiguxanthone-B (1) and 1,3,5,6-tetrahydroxy-2-prenylxanthone (2) (1:1 w/w). The xanthone mixture inhibited Staphylococcus aureus and Bacillus subtilis at a concentration of 6.25 µg/ml. When tested alone, the minimal inhibitory concentration of assiguxanthone-B was 25 µg/ml against B. subtilis. Kielcorin and 2,5-dihydroxybenzoic acid were inactive against both strains. None of the fractions was active against Escherichia coli or Pseudomonas aeruginosa. Viable cells of S. aureus were reduced by a 1-3 log CFU/ml within 12 h after exposure of one to eight times the MIC of the xanthone mixture. It is not known whether the tetrahydroxy-2-prenylxanthone or other components of the xanthone mixture are responsible for the main antibacterial activity or whether additive or synergistic action is involved

Naturally occurring pentaoxygenated, hexaoxygenated and dimeric xanthones: a literature survey

Peres,V.; Nagem,T. J.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/1997 Português
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This review gives information on the chemical study of 71 pentaoxygenated, 11 hexaoxygenated and 9 dimeric and more complex xanthones naturally occurring in 7 families, 29 genus and 62 species of higher plants, and 11 described as fern and fungal metabolites. The value of these groups of substances in the connection with the pharmacological activity and the therapeutic use of some species is shown. The structural formulas of 23 isolated compounds and their distribution in the species studied are given.

Antitumorigenicity of xanthones-rich extract from Garcinia mangostana fruit rinds on HCT 116 human colorectal carcinoma cells

Aisha,Abdalrahim F.A.; Abu-Salah,Khalid M.; Nassar,Zeyad D.; Siddiqui,Mohammad J.; Ismail,Zhari; Majid,Amin Malik Shah Abdul
Fonte: Sociedade Brasileira de Farmacognosia Publicador: Sociedade Brasileira de Farmacognosia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2011 Português
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This study aimed to investigate the antitumorigenicity of xanthones-rich extract from Garcinia mangostana L., Clusiaceae, fruit rinds which was obtained by a simple recrystallization of 75% ethanolic extract. α-Mangostin content of the extract was determined qualitatively by TLC and quantitatively by HPLC, and total xanthones content was quantified by UV spectrophotometry. The extract was evaluated for cytotoxicity, apoptosis and antitumorigenicity on HCT 116 human colorectal carcinoma cells. α-Mangostin was found to be the main constituent of the extract which was 71.2±0.1%, and the total xanthones content was 95±4.8% (wt/wt). The extract showed potent dose dependent cytotoxicity with IC50 value 9.2 μg/mL. Apoptosis studies revealed activation of caspases 3 and 7, DNA fragmentation, chromatin condensation and loss of mitochondrial membrane potential. Studies on cell migration and colony formation indicate reduced cell migration ability and clonogenicity of treated HCT 116 cells at sub-inhibitory concentrations. Taken together, the cytotoxic effect of the xanthones extract is mediated through the mitochondrial pathway of apoptosis. The reduced cell migration and clonogenicity of HCT 116 cells might prevent both primary and metastatic tumor growth in vivo which will be the topic of our future work using the metastatic orthotopic colon cancer model.

Xanthones from Vismia latifolia

Santos,Marcelo H. dos; Nagem,Tanus J.; Silva,Marilda C. da; Silva,Luiz G. F. e
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/10/2000 Português
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A new xanthone,1,4,8-trihydroxyxanthone (1,4,8-trihydroxy-9H-xanthen-9-one), was isolated from the roots of Vismia latifolia (Guttiferae). Four other known xanthones were isolated: 1,5-dihydroxy-8-methoxyxanthone, 1,7-dihydroxyxanthone, 1,6-dihydroxy-7-methoxyxanthone and 1,3,5,6-tetrahydroxyxanthone. The last two compounds were isolated for the first time from a Vismia species. The structures were established by UV, IR, MS, 1D and 2D NMR spectroscopic techniques.

Anti-Cancer Effects of Xanthones from Pericarps of Mangosteen

Akao, Yukihiro; Nakagawa, Yoshihito; Iinuma, Munekazu; Nozawa, Yoshinori
Fonte: Molecular Diversity Preservation International (MDPI) Publicador: Molecular Diversity Preservation International (MDPI)
Tipo: Artigo de Revista Científica
Publicado em 14/03/2008 Português
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Mangosteen, Garcinia mangostana Linn, is a tree found in South East Asia, and its pericarps have been used as traditional medicine. Phytochemical studies have shown that they contain a variety of secondary metabolites, such as oxygenated and prenylated xanthones. Recent studies revealed that these xanthones exhibited a variety of biological activities containing anti-inflammatory, anti-bacterial, and anti-cancer effects. We previously investigated the anti-proliferative effects of four prenylated xanthones from the pericarps; α-mangostin, β-mangostin, γ-mangostin, and methoxy-β-mangostin in various human cancer cells. These xanthones are different in the number of hydroxyl and methoxy groups. Except for methoxy-β-mangostin, the other three xanthones strongly inhibited cell growth at low concentrations from 5 to 20 μM in human colon cancer DLD-1 cells. Our recent study focused on the mechanism of α-mangostin-induced growth inhibition in DLD-1 cells. It was shown that the anti-proliferative effects of the xanthones were associated with cell-cycle arrest by affecting the expression of cyclins, cdc2, and p27; G1 arrest by α-mangostin and β-Mangostin, and S arrest by γ-mangostin. α-Mangostin found to induce apoptosis through the activation of intrinsic pathway following the down-regulation of signaling cascades involving MAP kinases and the serine/threonine kinase Akt. Synergistic effects by the combined treatment of α-mangostin and anti-cancer drug 5-FU was to be noted. α-Mangostin was found to have a cancer preventive effect in rat carcinogenesis bioassay and the extract from pericarps...

Structural Characterization, Biological Effects, and Synthetic Studies on Xanthones from Mangosteen (Garcinia mangostana), a Popular Botanical Dietary Supplement

Chin, Young-Won; Kinghorn, A. Douglas
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 01/11/2008 Português
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Mangosteen (Garcinia mangostana L., Clusiaceae) is a popular botanical dietary supplement in the United States, where it is used principally as an antioxidant. It is referred to as the “queen of fruits” in Thailand, a country of origin. The major secondary metabolites of mangosteen, the xanthones, exhibit a variety of biological activities including antibacterial, antifungal, antiinflammatory, antioxidant, antiplasmodial, cytotoxic, and potential cancer chemopreventive activities. Moreover, some of the xanthones from mangosteen have been found to influence specific enzyme activities, such as aromatase, HIV-1 protease, inhibitor κB kinase, quinone reductase, sphingomyelinase, topoisomerase and several protein kinases, and they also modulate histamine H1 and 5-hydroxytryptamine2A receptor binding. Several synthetic procedures for active xanthones and their analogs have been conducted to obtain a better insight into structure-activity relationships for this compound class. This short review deals with progress made in the structural characterization of the chemical constituents of mangosteen, as well as the biological activity of pure constituents of this species and synthetic methods for the mangosteen xanthones.

Xanthones from Mangosteen Extracts as Natural Chemopreventive Agents: Potential Anticancer Drugs

Shan, T.; Ma, Q.; Guo, K.; Liu, J.; Li, W.; Wang, F.; Wu, E.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 01/12/2011 Português
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Despite decades of research, the treatment and management of malignant tumors still remain a formidable challenge for public health. New strategies for cancer treatment are being developed, and one of the most promising treatment strategies involves the application of chemopreventive agents. The search for novel and effective cancer chemopreventive agents has led to the identification of various naturally occurring compounds. Xanthones, from the pericarp, whole fruit, heartwood, and leaf of mangosteen (Garcinia mangostana Linn., GML), are known to possess a wide spectrum of pharmacologic properties, including anti-oxidant, anti-tumor, anti-allergic, anti-inflammatory, anti-bacterial, anti-fungal, and anti-viral activities. The potential chemopreventive and chemotherapeutic activities of xanthones have been demonstrated in different stages of carcinogenesis (initiation, promotion, and progression) and are known to control cell division and growth, apoptosis, inflammation, and metastasis. Multiple lines of evidence from numerous in vitro and in vivo studies have confirmed that xanthones inhibit proliferation of a wide range of human tumor cell types by modulating various targets and signaling transduction pathways. Here we provide a concise and comprehensive review of preclinical data and assess the observed anticancer effects of xanthones...

Xanthones in Mangosteen Juice Are Absorbed and Partially Conjugated by Healthy Adults1234

Chitchumroonchokchai, Chureeporn; Riedl, Kenneth M.; Suksumrarn, Sunit; Clinton, Steven K.; Kinghorn, A. Douglas; Failla, Mark L.
Fonte: American Society for Nutrition Publicador: American Society for Nutrition
Tipo: Artigo de Revista Científica
Português
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The proposed health-promoting effects of the pericarp from mangosteen fruit have been attributed to a family of polyphenols referred to as xanthones. The purpose of this study was to determine the bioavailability of xanthones from 100% mangosteen juice in healthy adult participants (n = 10). Pericarp particles accounted for 1% of the mass and 99% of the xanthone concentration in the juice. The juice provided 5.3 ± 0.1 mmol/L total xanthones with α-mangostin, garcinones (C, D, and E), γ-mangostin, gartanins, and other identified xanthones accounting for 58, 2, 6, 4, and 5%, respectively. Participants ingested 60 mL mangosteen juice with a high-fat breakfast. Free and conjugated (glucuronidated/sulfated) xanthones were detected in serum and urine. There was marked variation in the AUC (762–4030 nmol/L × h), maximum concentration (113 ± 107 nmol/L), and time to maximum concentration (3.7 ± 2.4 h) for α-mangostin in sera during the 24-h collection. Similarly, xanthones in 24-h urine ranged from 0.9 to 11.1 μmol and accounted for 2.0 ± 0.3% (range 0.3–3.4%) of the ingested dose. There were no significant differences between female and male participants in mean pharmacokinetic values of α-mangostin in serum and urinary xanthones. Only 15.4 ± 0.7% of total xanthones in pericarp particles in the juice partitioned into mixed micelles during in vitro digestion. These results show that xanthones in mangosteen juice are absorbed when ingested along with a high-fat meal...

Biological Activities and Bioavailability of Mangosteen Xanthones: A Critical Review of the Current Evidence

Gutierrez-Orozco, Fabiola; Failla, Mark L.
Fonte: MDPI Publicador: MDPI
Tipo: Artigo de Revista Científica
Publicado em 13/08/2013 Português
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Mangosteen (Garcinia mangostana L.) is a tropical tree native to Southeast Asia that produces a fruit whose pericarp contains a family of tricyclic isoprenylated polyphenols referred to as xanthones. Numerous in vitro studies have shown that these xanthones possess anti-oxidant, anti-proliferative, pro-apoptotic, anti-inflammatory and anti-carcinogenic activities. Aggressive marketing of such health promoting benefits has resulted in mangosteen’s classification as a “superfruit”. This has led to sales of mangosteen containing beverages in USA alone exceeding $200 million in 2008 despite very limited animal and human studies. This review will (a) critically address recent reports of in vivo studies on the bioavailability and metabolism of mangosteen xanthones, (b) update the in vitro and in vivo data on anti-cancer and anti-inflammatory activities of mangosteen xanthones, and (c) suggest needed areas of inquiry regarding the absorption, metabolism and efficacy of mangosteen xanthones.

Novel Firmicutes Group Implicated in the Dechlorination of Two Chlorinated Xanthones, Analogues of Natural Organochlorines

Krzmarzick, Mark J.; Miller, Hanna R.; Yan, Tao; Novak, Paige J.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /02/2014 Português
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Although the abundance and diversity of natural organochlorines are well established, much is still unknown about the degradation of these compounds. Triplicate microcosms were used to determine whether, and which, bacterial communities could dechlorinate two chlorinated xanthones (2,7-dichloroxanthone and 5,7-dichloro-1,3-dihydroxylxanthone), analogues of a diverse class of natural organochlorines. According to quantitative-PCR (qPCR) results, several known dechlorinating genera were either not present or not enriched during dechlorination of the xanthones. Denaturing gradient gel electrophoresis, however, indicated that several Firmicutes were enriched in the dechlorinating cultures compared to triplicate controls amended with nonchlorinated xanthones. One such group, herein referred to as the Gopher group, was further studied with a novel qPCR method that confirmed enrichment of Gopher group 16S rRNA genes in the dechlorinating cultures. The enrichment of the Gopher group was again tested with two new sets of triplicate microcosms. Enrichment was observed during chlorinated xanthone dechlorination in one set of these triplicate microcosms. In the other set, two microcosms showed clear enrichment while a third did not. The Gopher group is a previously unidentified group of Firmicutes...

Vasodilator and antioxidant effect of xanthones isolated from brazilian medicinal plants.

Capettini, Luciano dos Santos Aggum; Campos, Lucas Vicente de Angelis; Santos, Marcelo Henrique dos; Nagem, Tanus Jorge; Lemos, Virg?nia Soares; C?rtes, Steyner de Fran?a
Fonte: Universidade Federal de Ouro Preto Publicador: Universidade Federal de Ouro Preto
Tipo: Artigo publicado em periodico
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Vasorelaxant and antioxidant activities are important in the therapy for cardiovascular diseases. We aimed at investigating the vasorelaxant and antioxidant activities of six xanthones iso-lated from Brazilian medicinal plants. Xanthone ( 1 ), 1-hydroxy-xanthone (2 ), 4-hydroxyxanthone (3 ), 1-hydroxy-8-methoxy-xanthone (4 ), 1,3-dihydroxy-7-methoxyxanthone ( 5 ) and 2,6,8-trihydroxy-1-methoxyxanthone ( 6 ) induced concentration-de-pendent vasorelaxant effects in endothelium-intact mice aortic rings. The presence of a hydroxy group in position 1 seemed to decrease the vasodilator effect while a hydroxy in position 4 and an increased number of hydroxy groups improved the vaso-relaxatory potential of xanthones. All xanthones showed antiox-idant activity but their potencies did not correlate with the vaso-dilator effect. Our results suggest that the tested xanthones are potentially vasorelaxant and antioxidant compounds but the two activities are not interrelated.

Trioxygenated naturally occurring xanthones

Peres, Valdir; Nagem, Tanus Jorge
Fonte: Universidade Federal de Ouro Preto Publicador: Universidade Federal de Ouro Preto
Tipo: Artigo publicado em periodico
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This review discusses the chemistry of 127 trioxygenated xanthones occurring in six families, 37 genera and 107 species of higher plants, and 55 which are fungal or lichen metabolites. The value of these substances in connection with their pharmacological activity and the therapeutic use of some species is considered.The structural formulae of 130 compounds and their natural distribution are given

Xanthones and coumarins from Kielmeyera lathrophyton

Cruz,Frederico G.; Silva-Neto,José T. da; Guedes,Maria L. S.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2001 Português
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Three xanthones and six coumarins were isolated from the hexane extract of the stems of Kielmeyera lathrophyton, among them two new prenylated xanthones 1,5-dihydroxy -6'-methyl -6' -(4-methyl -3-pentenyl) -pyrano(2',3':3,2) -xanthone, 1,7 -dihydroxy -6' -methyl -6' -(4 -methyl -3 -pentenyl) -pyrano(2',3':3,2) -xanthone, and two new 4 -s -butylcoumarins 7 -hydroxy -8 -(3-methyl -1 -oxobutyl) -4 -s -butyl -6',6' -dimethylpyrano (2',3':5,6) -coumarin, 7 -hydroxy -8 -(2-methyl -1 -oxobutyl) -4 -s -butyl -6',6' -dimethylpyrano (2',3':5,6) -coumarin, along with the compounds, delta -tocotrienol, friedelin, 24alpha -ethylcholest -5 -en -3 -one, and , 24alpha -ethylcholest -5,22 -dien -3 -ol. These compounds were identified by comparison with literature data, and their spectroscopic properties.

The Genus Buellia Sensu Lato in the Greater Sonoran Desert Region: Saxicolous Species with One-septate Ascospores Containing Xanthones

Bungartz, Frank; Elix, John; Nash, Thomas
Fonte: American Bryological and Lichenological Society Inc. Publicador: American Bryological and Lichenological Society Inc.
Tipo: Artigo de Revista Científica
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Six species of saxicolous Buellia s.l. containing xanthones are reported from the Greater Sonoran Desert Region: Buellia concinna, B. halonia, B. mamillana, B. prospersa, B. subaethalea, and B. trachyspora. All species have a pale yellow to greenish yellow thallus characterized by the presence of xanthones. Nevertheless, they all show distinct characters and may consequently only be distantly related. Buellia concinna, a taxon previously reported only from Europe, is the valid name for the North American B. semitensis. Buellia subaethalea, first described by Bouly de Lesdain, but subsequently largely ignored, is reported for the first time from the region. Buellia trachyspora, a subtropical species barely reaching the Sonoran Region, is distinguished from B. mamillana.